Joseph Lister

“ It is matter for discussion how inflammatory congestion is brought about by nervous action. It may be doubted whether active congestion could alone give rise to it, though it is by no means inconceivable that the excessive supply of the nutrient fluid might in time exhaust the tissues by over-stimulation, and so bring about more or less of that impairment of vital energy which we have seen reason to regard as the essential cause of the blood-corpuscles lagging behind the liquor sanguinis. ”

“ For adhesiveness of corpuscles is not occasioned in the frog's web by amputation of the limb; nor is it produced in the human subject by complete detachment of a portion of tissue; as is clearly shown by the persistent healthiness of a piece of skin entirely transplanted in skin-grafting. We are therefore forced to the conclusion that the adhesiveness of the red discs in the horse's jugular, as contrasted with its complete absence in the vein of the bat's wing, was due to the larger size of the vessel in the former case. ”

“ In thinking over this striking difference between the effects of the two kinds of suture, it seemed to me clear that it depended on the silk imbibing blood and serum, which, undergoing decomposition in its interstices, grew more irritating the longer the process continued; whereas the metal gave no hold to the organic liquids, which were shed unaltered as fast as they were effused. From these and other analogous considerations, I taught my class at that time that decomposition of the organic liquids was the essential cause of suppuration. ”

“ A very interesting observation which I made long ago, but to which I have not before directed attention in this point of view, shows that an extreme degree of adhesiveness of the red discs may exist within a blood-vessel the walls of which are in perfect health with reference to coagulation. If a horse's jugular vein, obtained in the manner I have described, is suspended vertically, the blood in it remains fluid for an indefinite period, hut the red corpuscles soon fall from the upper parts of the fluid, leaving a huffy layer of plasma, readily seen through the translucent wall of the vessel. ”

“ Yet from the very happy circumstance of the conspicuousness of the pigment, the results of their activity could be observed with the utmost facility, and their behaviour in relation to inflammatory congestion easily studied even under a low magnifying power.
The pigment cells pervade the skin and subcutaneous tissue of which the frog's web consists, and are especially numerous about the blood-vessels, round which their branches twine abundantly. They must, therefore, be acted on along with the vascular parietes by anything applied to the surface of the membrane. ”

“ Our fathers would have been greatly astonished to learn that the chlorophyl grains of vegetables were, as has been shown in recent years, living organisms, multiplying by division like the nuclei of their containing cells: and though the pigment granules are much smaller, they must be greatly surpassed in minuteness by many microbes which, though hitherto invisible to us, we believe from analogy to be the causes of some infective diseases. ”

“ A sharp knife does not destroy any part of the tissues, hut it throws them in a microscopically thin layer into a state of intense inflammatory congestion, attended with effusion of coagulable liquor sanguinis. But this noxious agency is only momentary in its operation. It has no time to cause active congestion through the nervous system, but at once leaves the injured tissues free to recover by virtue of their own inherent powers. If the instrument be very sharp the layer of lymph will be very thin, unless some other disturbing cause come into play. ”

“ The tissues, as distinguished from the blood, were therefore the parts primarily and essentially affected by the action of the irritant. And we have seen that, in their relation to the blood-corpuscles, they approached more or less closely, according to the degree of the irritation, the behaviour of ordinary solids, such as glass, as distinguished from the living structures. The natural inference was that they had lost more or less, for the time being, certain special properties which they possessed when in active health as constituent structures of the living body. ”

“ A hood of black cloth, carefully arranged so as to exclude light from the eyes without obstructing respiration, entirely prevented a dark frog from becoming pale in bright sunlight. I was naturally desirous of ascertaining through what efferent channels the nervous impulse that caused concentration of the pigment on exposure to light was conveyed from the brain to the foot. Division of the sciatic nerve had no effect whatever upon the colour of the limb. I then tried cutting through all the structures in the thigh except the bone, the femoral artery and vein and the sciatic nerve. ”

“ But in some animals, e.g., the horse, the adhesiveness of the discs is so great that they stick to one another by the parts that come first into contact, producing dense spherical masses large enough to be visible to the naked eye, like grains of red sand. These, falling rapidly through the lighter plasma, leave the upper part of the liquid free from red corpuscles before coagulation occurs, thus giving rise to the huffy coat, whereas in the cow the delicate network of rouleaux remains suspended, and no buff occurs. ”

“ I used to illustrate to my class by a simple experiment the enormous increase which takes place in the pressure of a liquid upon the walls of a tube through which it is flowing, when an obstacle is opposed to its passage. When, therefore, the corpuscles begin to block the capillaries the plasma will naturally be forced in undue quantity through their porous walls.
When inflammation assumes an intense degree, the effused liquor sanguinis has the peculiarity of being coagulable, producing by its solidification the characteristic "brawny" swelling of the parts among which it is poured out. ”

“ Now we know, from the experiment with the ox's jugular, that coagulation is propagated with extreme slowness, if at all, from a clot in blood perfectly undisturbed. The earlier coagulation of the main mass of the stirred blood was, therefore, not caused by propagation of the process from a layer upon the surface of the jar, but must have been the result of the brief agency of the glass rod. ”

“ The coagulation of the blood, while it is a matter of fundamental importance in physiology, has peculiar interest for the surgeon, on account of the special feature of coagulability of inflammatory exudations and the part played by lymph in the healing of wounds and various other pathological phenomena, such as the sealing of divided arteries by blood-clot. ”

“ Adhesiveness of corpuscles and coagulation are both brought about by the operation of noxious agents upon the tissues of the part concerned. But it by no means follows that they are in all respects analogous phenomena. We have seen that normal blood has no innate tendency to coagulate, and needs no action of the tissues upon it to ensure its fluidity. But the blood-corpuscles may he naturally adhesive bodies, possessing a viscosity only kept in abeyance by some influence exerted upon them by the living tissues in their vicinity: and such appears to he really the case. ”

“ An experiment that greatly pleased Dr. Sharpey would seem to indicate that the vaso-motor function for the hind legs is also discharged by the most anterior part of the cord. A frog having been arranged as before described, the point of a fine needle, curved at the end, was introduced into the wound behind the occiput, so as to prick for an instant the divided medulla. The eye of the observer being over the microscope while this was done, the arteries of the web were seen to contract to complete obliteration of calibre, as in the first experiment with warm water. ”

“ Greatly as they differ in their nature, whether physical, as mechanical violence, heat, and the electric shock, or chemical of the most varied characters, one feature they have all in common; if pushed far enough they destroy the tissues on which they act. Extreme inflammatory congestion is the state which they produce when their action is just short of the lethal degree; and it could hardly he doubted that the state of the tissues just short of death must be one of impairment of vital power. ”

“ Under intense irritation the capillary walls will naturally be affected by the noxious agency as the veins of the sheep's foot were by the constricting cord, and, like them, will act upon their contained blood as if they were ordinary solids. The plasma of that blood will therefore receive from the blood-corpuscles the material requisite for forming fibrin, and, passing through the pores of the capillaries with that addition, will constitute a coagulable exudation. ”

“ In whipped horse's blood the red discs aggregate into dense masses as in blood freshly drawn, and falling rapidly soon leave a deep layer of serum. In whipped cow's blood, rouleaux forming in the serum as in the plasma, there will be found, if the animal was healthy, only a thin superficial serous layer, even after the lapse of 24 hours. ”

“ Active congestion, or arterial dilatation with consequent free flow of blood through the capillaries, is an early and prominent symptom of inflammation of a vascular part in man. Unlike the morbid condition which is produced by the application of irritants to the frog s web, it is brought about indirectly through the nervous system. ”

“ In the red corpuscles the tendency to mutual adhesion shows itself in different forms according to the species of the animal or its state of health. In the frog the prominence of the nuclei leads to very irregular grouping of the oval cells. In man the biconcave circular discs adhere under normal circumstances in that position which enables their moderate degree of adhesiveness to come best into play, the result being the well-known "rouleaux." The same is seen in the healthy blood of the cow. ”

“ In a narrow ring round the mustard, where the volatile oil could only act extremely mildly on the web, the stellate condition gave place to complete diffusion; whereas under the mass, where the irritant had acted at once with full energy, the stellate appearance remained unchanged. Inflammatory congestion, however, had been produced in the ring of full diffusion as well as in the more strongly irritated area. It happened that complete concentration afterwards took place in the rest of the web, while the irritated areas retained the appearances above described. ”

“ Facts such as those which I mentioned as having aroused my interest in my student days in a ease of pyæmia, made such a view to me incredible, and I determined to ascertain, if possible, the real state of things by experiment. I introduced into a vein of a living horse a short glass tube open at both ends, containing a piece of silver wire in which was mounted a little hit of calico, which I thought likely to give rise slowly to putrefactive change; shutting off the portion of vein concerned from the general circulation by means of ligatures. ”

“ On the other hand, if irritation is less severe, although the corpuscles acquire more or less adhesiveness, involving corresponding obstruction to the flow through the capillaries and consequent undue passage of liquor sanguinis through their walls, the constituent tissues of the vessels are not reduced to the condition in which they act like ordinary solids in relation to coagulation. This seems to follow from the uncoagulable character of the effused fluid. For we know that what used to be termed the serum of œdema or hydrocele is simply the normal plasma. ”

“ It .seems probable that the diffusion under the slighter irritation may have been the result of the nerves in the irritated part being paralysed before the pigment cells.
As is commonly the case with more specialised structures, the pigment cells are a delicate form of tissue, and are more readily killed than other constituents of the web. Hence, if care is not taken to avoid pushing the action of the irritant too far, it will be found, after resolution has taken place, that the pigment cells never recover ”

“ If, on the other hand, in securing the frog for observation under the microscope, scrupulous care was taken to avoid needless exposure of the foot to the warmth of the hands, the threads for fixing the toes being tied by means of long forceps, and each half of the knot done separately, with a fair interval between them, a state of the circulation was seen which is, I believe, even to this day rarely witnessed. ”

“ Or it may be that the nerves produce this weakening effect upon the tissues by immediate action upon them. From that point of view, the proof afforded by the pigment cells of the influence of the nerves over processes going on within cells seemed to me peculiarly interesting. And we can conceive of nervous impulse impairing their energies either by over-stimulation followed by exhaustion, or by immediate prostration of their powers as by an electric shock. ”

“ In spite of hot applications to the skin—which sometimes work like a charm in such circumstances, operating, as it would appear, by distracting, so to speak, the attention of the nervous system from the affected organs—that man died within a few hours of the rigor. ”

“ I must content myself with stating the conclusion to which I was led at the time I am speaking of, and which was confirmed by later investigation, viz., that the introduction of septic material into a vein may give rise to the rapid development of large nucleated cells which, growing at the expense of the original constituents of the coagulum, convert it entirely into a thick yellow liquid. ”